Honduras Marine Science Report

Transcription

1 Honduras Marine Science Report Report written by Dr James Saunders, Jonathan Shrives, Jessica Harm, Steve Green and Natalie Bown based on research from Operation Wallacea volunteers

2 Contents Executive Summary 3 1. Introduction Cayos Cochinos Utila Social Development Team Research Groups 6 2. Locations of Study Utila Cayos Cochinos East End Chachahuate La Ceiba Rio Estiban Neuva Armenia Fish and Invertebrate Ecology Research Group Introduction to the group Project introduction and rational Methods Results Conclusions Publications Sea Urchin Ecology Research Group Introduction to the group Project introduction and rational Methods Urchin Surveys Urchin / parrotfish interactions and microscale habitat variation surveys Feeding preference of reef urchins Results Urchin abundance Urchin/Parrotfish interactions Microhabitat preference Feeding trials Conclusion Survey results Habitat preference Urchin/Parrotfish interaction Feeding preference Publications 27 1

3 5. Mangrove Ecology Research Group Introduction to the group Project introductions and rationales The effects of pollution and disturbance on the health of mangrove systems Introduction Methods Results Discussion Sediment stabilisation and sequestering Introduction Method Results Conclusion Relationship between mangrove system health and function as a reef fish nursery Introduction Method Results Discussion Overall Discussion Herpetofauna Research Group Group Introduction Bay Island Boas Project Introduction and Rational Methodology Results Discussion Black-Chested Ctenosaur (Ctenosaura melanosterna) Introduction Methods Results Discussion Publications Overall Conclusions The Cayos Cochinos Utila Summary 48 2

4 Executive Summary Operation Wallacea operates a multidisciplined marine research program in Honduras. This comprises of research stations within the Cayos Cochinos Archipelago and the island of Utila, working in partnership with the HCRF and the Coral View Research Station respectively. In addition a mobile social science team operates within communities on the north shore of the mainland. Within these research stations five research groups operate, these groups are the Fish and Invertebrate Ecology Research Group, the Urchin Ecology Research Group, the Mangrove Ecology Research Group, the Herpetofauna Research Group and the Social Development Group. Research conducted over the summer expedition of 2008 by these groups covered many elements of marine conservation. These included surveys of the reef fish and urchin populations, mangrove system health and functioning, endemic reptile species and of attitudes and opinions in the local communities towards sustainable development, in particular ecotourism. In addition research into the ecology and behaviour of urchins, reef fish, boa constrictors and mangrove systems. General results of the work indicate that the marine environment is subjected to a variety of different stresses and threats, in particular over fishing and destruction and degradation of habitat. Despite this the status of the marine environment is currently in a position that while the impacts are evident they are not at a terminal level. For example fish populations, specifically certain species, are low but they are at levels from which recovery is possible, likewise there are several areas where mangroves have been destroyed or subjected to high levels of disturbance, but the mangrove systems are still fulfilling vital functions while large areas of mangroves remain pristine. The work done in the 2008 has developed the research program established over the previous year by Operation Wallacea in Honduras and has placed the work into a framework of research and monitoring of the marine environment around the Cayos Cochinos and Utila in addition to working in the local communities to ensure they benefit from development in the area. The ongoing monitoring of the marine environment is of paramount importance so the health of the systems can be gauged, either to protect against its destruction or to provide data to substantiate protection zones or policies. 3

5 1. Introduction Operation Wallacea has been associated with Marine Research in Honduras since The program, which started in the Cayos Cochinos archipelago, has now developed to encompass five research groups in a number of locations in the Honduran Bay Islands and on the mainland in addition to various associations with local and national groups within Honduras. The basis of Operation Wallacea s work is to bring academics and world leaders in research topics into the field to run small specialist research groups within the overall project framework. These groups consist of principle researchers, Ph.D. students, dissertation and thesis students and research assistant volunteers. The projects run over a 10 week period every summer. This format gives many advantages to field research such as bringing together a wide variety of multidisciplined field scientist with varied backgrounds into the same place with a central organisation coordinating the research. Funding for the research is entirely based on volunteers, this ensures that projects can be run over prolonged periods and datasets can be built up over many years, a situation often prohibited by time scales for grant funding. The research is based on collecting data on the local ecosystems that can be channelled into high quality research publications and grant applications to establish examples of best practice conservation in the local communities. The marine research and conservation objectives of Operation Wallacea in Honduras often require a multidisciplinary approach, utilising expertise from a variety of research backgrounds or data collection from a variety of locations. To achieve this Operation Wallacea has established three independent research operations within the marine program. Two of these are based at permanent research centres and concentrate on studying the biodiversity and ecology of the local marine and terrestrial ecosystems. The first of these is run from the Marine Research Station the island of Cayo Menor within the Cayos Cochinos Marine Protected Area (CCMPA) and the other is based at the Coral View Research Centre on the island of Utila. The third operation is a mobile social development research team who travel around various villages and towns on the mainland and Islands, including both of the permanent research sites, conducting research on developing a sustainable livelihood for the local communities. Results from this group are considerable and are covered separately in the Honduran Marine Social Development Report Projects run within the marine program can be based solely within one of the three research operations or involve two or all three of them. A description of the three operations follows with the collaborators, main research aims and development objectives of each listed (Section 1). Descriptions of the locations in which Operation Wallacea operates are then outlined (Section 2) before the research is detailed by research group (Sections 3-6) and summarised in a final conclusion (Section 7). The following report is a summary of the research conducted by the Marine Research Program in Honduras in the summer of Cayos Cochinos The Cayos Cochinos Islands were established as a Honduran National Monument in 1993 and given protection through the establishment of the Cayos Cochinos Marine Protected Area (CCMPA) at the same time under the management of the newly established Honduran Coral 4

6 Reef Foundation (HCRF). Operation Wallacea started working with the HCRF within the CCMPA in 2003 at the Marine Research Station situated on Cayo Menor. The main objectives of the research within the CCMPA are; Yearly monitoring of the status of the reefs within the Marine Protected Area, to determine the health of the reef system and the success of the CCMPA in protecting the reef systems. Conducting high quality marine and terrestrial research within the MPA, producing publications suitable for peer review and establish the Cayos Cochinos MPA and Marine Research Station as an internationally recognised centre for quality marine research. Assess the population levels, ecology and behaviour of the native Bay Island Boa Constrictor and Ctenosaurs on the two main islands. 1.2 Utila Operation Wallacea started operating on Utila in 2006 and is in the process of developing a long term monitoring and research program on the Island. This is being done in collaboration with Coral View Research Centre from which all accommodation, research and diving operations are run. The program has been built on in subsequent years since its conception. The collaboration has the following main objectives; Ecological Establish a yearly monitoring program of the status of the coral reefs around the Utila, to be conducted every year with the data used to produce a Status of the reefs on Utila - annual report. Establish a long term monitoring program of the mangrove systems on Utila and use the data to promote the conservation of these systems. Conducting high quality marine and terrestrial research around Utila, producing publications suitable for peer review and establish the Coral View Research Centre as an internationally recognised centre for quality research. Interaction with local parties Develop the Coral View Research Centre into a high quality marine research centre, suitable for Operation Wallacea research during the summer season, University class group trips throughout the year and establish the centre as a the recognised ecotourism facility on Utila through programs such as a reef ecology week and promoting reef awareness. Develop a relationship with the Bay Island Conservation Association (BICA) through which the monitoring and research work can be disseminated through local and national bodies in order to promote the conservation and sustainable utilisation of the biodiversity of Utila. 5

7 1.3 Social Development Team The social development team undertake a variety of projects based in communities on the mainland, predominantly Rio Esteban, Neuva Armenia and La Ceiba, the two communities of West End and Chachahuate within the Cayos Cochinos MPA and East Harbour on Utila. Although the specifics of the individual projects dictate if and for how long each student spends in each community. The social science team involves interaction with several local organisations, these include HCRF on Cayos Cochinos, and Tony Ives, Director of the Groupo Apoyo y Desarollo (GAD - Development Support Group), a NGO based in La Ceiba that works to promote sustainable development and scholarships to the communities on the North Shore and within the CCMPA. The Research Group also recruits students from the University in La Cieba, the Centro Universitario Regional del Litoral Atlantico (CURLA) to act as translators. The social science group has a varied remit, assessing various elements of community development within the places they visit. These can roughly be divided into four components Develop an ecotourist industry within Rio Esteban Assess the feasibility of sustainable development on Neuva Armenia Assist in the commercialisation of the MPA Assess the attitude within the communities to the development of the MPA and other related topics 1.4 Research Groups Within the three operations there are currently 5 research groups; Fish and Invertebrate Ecology Research Group Urchin Ecology Research Group Mangrove Ecology Research Group Herpetofauna Research Group Social Development Group 6

8 2. Locations of Study Bay Islands 2.1 Utila Utila is the smallest of the three Bay Islands off the north coast of Honduras. The island is roughly 13Km long by 4Km wide and covers an area of approximately 45Km 2. The island is situated 27Km north of La Ceiba making it the closest of the Bay Islands to the mainland. The island is an international recognised dive tourist destination, specialising in dive training in addition to a popular tourist destination on the backpacking trail. The population centre on the island is East Harbour, although it is often just know as Utila. However, with the growing tourist industry developments are spreading around the shoreline, especially on the south coast, although inland development is limited. Inhabitants and Culture The Island was under British sovereignty until the mid 1800 s and many influences of this are still evident, including English as the dominant language, and the island has a distinctly Caribbean atmosphere in comparison to the Central American cultures of the mainland. The population of Utila, roughly 7000 people, comprise a variety of different groups. The Garifuna have inhabited the island for many generations and within a few families own a large portion of the land. There is also a large population of Caucasian Caymanian Hondurans who have remained on the Island and Cayes from when the Bay Islands were a British colony. Since the rapid expansion of the dive industry Utila s population has grown to include sizable populations of Hispanic Hondurans from the mainland who have come to the island to work. In addition Utila also accommodates a large number of tourists and visiting workers who may visit the island for only a few days or stay on a semi-permanent or permanent basis for months or years. Geography and biodiversity of the Island The town of East Harbour spreads along the coastline in a natural bay in the south east of the island, behind which lies the only raised land, comprising of Pumpkin Hill and Stewarts Hill, the remainder of the island stretches to the west and is mostly lagoons, mangroves and wetlands. In total the island is 70% mangroves and associated wetlands. At the far west of the island are the Cayes, low lying small islands of varying size from very small to large enough to accommodate a small community. The mangrove forests on Utila are largely comprised of the red mangrove species Rhizophora mangle, although inland black and white species are also found. Within the mangroves are found a wide variety of fauna commonly associated with Caribbean mangrove systems, as well as an indigenous species of iguana called the Swamper that is only found on Utila. The north and south shores and shallow subtidal zones of Utila have very different habitats. On the sheltered south side of the island there are extensive seagrass beds, extending from the intertidal zone to the reefs. The reefs are mostly between 5 and 25 metres in depth and mostly made of reef walls. There are few shallow areas that can be classified as reef flats. The south shore is the site of most of the commercial building and large areas of the shore have been developed. The entrances to the two main lagoon systems on the island, Big Bite Pond and Oyster Bed Lagoon, are situated on the south shore. The edges of both of these 7

9 lagoons are nearly entirely covered in mangroves, with most exceptions occurring where development has resulted in their destruction. The North and Eastern shores of Utila face the prevailing wind and waves making them more exposed in nature. Reefs on the North shore are mostly steep drop offs, from 5m up to 50m+ in some cases. The shore is a mixture of sandy beaches, exposed rocks (called iron shore) and mangroves. There is small but isolated developments on the north shore. The north shore has two large semi enclosed bays, called Rock Harbour and Turtle Harbour. Turtle Harbour is a protected area, which encompasses the mangroves, seagrass and reefs out from the shore. View of East Harbour from Chepes Beach, Utila Economy The island has experienced extremely rapid development of dive tourism over the previous years, resulting in 11 dive schools on the island and numerous hotels, restaurants and associated developments. The dive and tourist industry comprises up to 90% of the economy of the island and its growth has resulted in a large increase in the population of the island, including mainland Hondurans coming for work and a sizeable tourist population that remain on the island on a permanent or semi-permanent basis. The remaining industry is mostly related to the fisheries on the reefs and pelagic zone. This is mostly based on the Cayes where the tourist industry is not as prevalent as it is on the main island. Areas of research interest The dive tourism has had a massive impact on the ecology of the island. The development has mostly occurred in the low lying land near the shore and has resulted in the removal of large areas of mangroves. All development has been performed with little consideration of environmental impact and as a result there is a large level of mangrove destruction in the developed areas. Additionally the development has outpaced the growth of the islands infrastructure resulting in large levels of pollution entering the water. This is also true of sediment transport that has increased dramatically as a consequence of the loss in mangroves and is probably resulting in increased sedimentation on the reefs adjacent to the mangrove lagoons. The fishing industry is having a huge impact on the reef fish populations around Utila, although evidence for this is mostly anecdotal. Many commercially important reef fish hold important positions within the reef ecosystem, usually as a predator, and their removal could have severe consequences for the health of the reef system. 8

10 2.2 Cayos Cochinos The Cayos Cochinos Islands are located about 18km off the northern Honduran shore and comprises the very southern end of the Meso-American Barrier Reef System (MBRS), the second largest barrier reef in the world. The islands and surrounding seas were designated as a National Marine Monument by the Honduran Government in 1993 and remains the only such area in Honduras. The islands have been established as a protected area by the Honduran Government under the banner of the Cayos Cochinos Marine Protected Area (CCMPA) and managed by the Honduran Coral Reef Foundation (HCRF). This agreement established specific protection for the reefs and the wildlife on the islands. These included a limit on fishing in volume and species and established protection for the indigenous reptile species on the islands. The protection of the Cayos Cochinos islands was formed in partnership with the publication of the management plan which main objectives included the protection of the reefs and terrestrial systems and ensuring that the income lost to the fishing villages through the loss of their fishing grounds was compensated through the establishment of alternative incomes. The Marine Protected Area The Cayos Cochinos Marine Protected Area (CCMPA) is based around an archipelago of small islands and shallow seas. There are two main islands within the area, Cayo Mayor and Cayo Menor. Cayo Mayor with a width of 1.8km and length of 1.7km is slightly larger than Cayo Menor that has a width of 1Km and length of 1.3km. In addition to these two main islands there are 13 small Cayes within the archipelago. The CCMPA contains a wide variety of marine habitats, with reefs to depths of 30m+, extensive seagrass systems and large areas of bare sediment. These habitats are distributed around the park, often nearer the islands and cayes, although several shallow reefs are found in the open sea. Despite this diversity of habitats and islands the reserve does not have a significant mangrove system, with only a few trees found on Cayo Mayor within the MPA. Settlements and industry Cayo Mayor has a resident population year round, with a small artisan fishing community in East End in addition to a small hotel called the Plantation Beach Resort and several private homes. Cayo Menor has no local communities or industry and has been preserved solely for research purposes. This research is based at a small research centre that contains a dive centre, laboratory facilities, several permanent accommodation buildings and catering facilities. The only long term residents on the island are a handful of Navy guards and occasional researchers. The other settlement within the CCMPA is another fishing community on Cayo Chachahuate. The industry of the area was largely based on artisan fisheries based in the two communities of East End and Chachahuate, these have both been heavily impacted by the restricted fishing rights dictated by CCMPA management plan. However, part of this plan established ensures that alternative East End on Cayo Mayor 9

11 income sources were established for these communities, and those on the North Honduran Coast, to compensate for the loss of revenue from fishing activity. This has involved the promotion of ecotourism and the research station in the area. The Islands are now also used as the setting for the Survivor television series in both Italy and Spain, the income of which is considerable. Areas of research interest The Cayos Cochinos Islands offers a wide variety of marine and terrestrial habitats for surveys and experimentation, this allows a variety of unique research opportunities within the area. Of particular interest is studying the success of the CCMPA, and the various fishing restrictions that apply to different species and areas of the park. This includes both fish and commercially and ecologically important invertebrate species. The long term arrangement between Operation Wallacea and the HCRF gives a rare opportunity to collect long term data sets over many years that may reflect the status of the CCMPA or possibly larger scale patterns such as global warming and an impact assessment should the islands be hit by a hurricane. 2.3 East End East End is the sister community of Rio Esteban, situated on the north side of Cayo Menor. The community has an approximate population of 22 residents living in 19 houses along a single 200metre stretch of beach, peaking to a maximum population of 90 during the fishing season (April-September). The community has one primary school with two classrooms that serve all of the MPA. The area also has a Honduran Navy station where the four Navy personnel employed to patrol the MPA reside. East End has some tourism development, receiving US AID funding in 2007 to build cabanas and a restaurant. These were ready for use in summer 2008 and were used by both the Operation Wallacea social science and Herpetofauna Research Groups. The immediate marine environment consists of inner reef flats of approximately 3 metres in depth and a gently sloping wall of about 22 metres. 2.4 Chachahuate Chachahuate is the sister community of Nueva Armenia, occupying the largest of the cayes within the CCMPA ( N, W). There are approximately 43 households with a maximum population of 200 during the peak fishing season, and an average resident population of 90 people. The island has reduced in size following Hurricane Mitch in 1998, to about 50 metres in length because it is exposed to the prevailing north easterly trade winds. There is some tourism development with US AID and WWF sponsorship of a restaurant and cabanas, and the island is advertised in the national tourism guide Honduras Tips. Commercial sail boats, located in Roatan and Utila advertising day long trips to the Cayos Cochinos Seaside Beach and tourist restaurant on Chachahuate 10

12 islands, use Chachahuate as the island stop off. The reef flat is approximately 1metre deep, sloping gently to a 20 metre wall and sandy bottom. Part of the recent development of the island was the construction of two environmentally friendly toilets in 2007 to replace the long drop toilets that had been used in the past and were resulting in localised organic pollution. These were not being used as successfully as desired in 2007 however their use has now become common. Mainland 2.5 La Ceiba The largest city on the north Honduran coast and the third largest city in the country, La Ceiba has a population of roughly people. La Ceiba is a frequent destination for tourists as it is the main point of access to the Bay Islands either by air or sea as well as being local to a variety of ecotourism centres in the local area, including several based in the Pico Benito National Park. It is also the transport centre for many villages on the northern Honduran coast with road access and many regular bus services. The city is the location of the HCRF, which has quick access to the CCMPA via the port, and the location of government agencies departmental offices that have institutional and legal responsibility for the marine environment. One such important government department, DIGEPESCA, has the duties of monitoring all fishing activity within the Department de Atlantida region; issuing commercial and artisanal fishing licences; and recording the supply of goods and their prices. La Ceiba was badly affected by Hurricane Mitch in 1998, and has frequent flooding problems during the wet season. 2.6 Rio Estiban Rio Esteban is a small Garifuna settlement furthest from the main city of La Ceiba on the north coast of the sites studied, approximately 12 nautical miles from the CCMPA. The community has an estimated 630 inhabitants divided into several neighbourhoods (barrios), with one school up to secondary level. The coastal region is an area of estuarine discharge from the River Aguan, mangrove forests and mud flats creating an environment of relatively high deposition with a natural spit. The community has relatively little tourism with four small hotels, five restaurants (including a newly developed beachfront restaurant), and cabanas on the beachfront that are now abandoned as a result of Hurricane Mitch in It is the least accessible of all the study sites, requiring an off-road vehicle to navigate through a riverbed during the dry season. During the wet season this river bed is prone to flooding and prevents any access to or from the community. The community does have a regular daily bus service to Jutiapa and Trujillo; however, these buses cannot pass through the river when in flood. Very recently in 2007, the Municipality of Colon agreed to erect a bridge over the River Esteban, due for construction in Heavy flooding has subsequently destroyed this bridge and the community remains isolated during periods of high rainfall. In 2008 Operation Wallacea started using Rio Esteban as the entrance point to the CCMPA. This involved volunteers being accommodated in local houses for one night. A cultural event, food and transportation to the CCMPA on fishing boats were also arranged through the village. 11

13 2.7 Neuva Armenia Nueva Armenia is a relatively large Garifuna settlement on the north coast mainland, approximately 40km from La Ceiba. The community has an estimated 3000 inhabitants dispersed into distinct neighbourhoods, with two schools up to secondary level, a medical centre, several churches and a fish freezing plant, although this has been un-operational since There is a relatively low level of tourism with two hotels and three restaurants, and organised boat trips out to the Cayos Cochinos. It is accessible with regular daily bus services to Jutiapa and La Ceiba, and a purpose laid gravel road. The community is now split by the River Aguan which changed its course because of the severe flooding caused by Hurricane Mitch in As a result of the hurricane, new municipal housing has been built to re-house displaced members of the community. The immediate coastal zone has a tidal sand bar, mud flats and fluvial run-off. The coastal area is used as the entering point by some tourists to the CCMPA and until last year was used by Operation Wallacea. 12

14 3. Fish and Invertebrate Ecology Research Group Personnel Senior Scientist - Project supervisor - Dissertation projects - Dr. James Saunders - Operation Wallacea Jessica Harm - Oxford University Edward Mansel Lewis - Newcastle University Mikka Haig - Oxford University Jane Plunton - Northumbria University 3.1 Introduction to the group The Fish and Invertebrate Ecology Research Group is based on both the Cayos Cochinos and Utila. On both systems the health of the reefs have huge ecological and economic importance to the area and therefore assessing the health of the fish and invertebrates is of considerable importance, as is developing an understanding of their ecology. The group mostly focuses on species of fish and invertebrates that are commercially important to the systems or can be used as indicators of overall reef health. In 2008 the group conducted extensive surveys of the fish populations around both locations, using data to assess the status of the CCMPA around the Cayos Cochinos and establishing the framework for a long term monitoring program on the reefs around Utila. 3.2 Project introduction and rational Fish and invertebrate populations are both highly important to the status of the reefs and the economy of the local area. On the Cayos Cochinos this economic importance is mostly based on the fishing communities that surround the CCMPA and are allowed limited fishing rights within the park. On Utila economic importance is also based on the fishing industry but more significantly the large dive tourist industry based on the reef around the island. Fish and invertebrate populations provide both an income source to both areas in addition to performing vitally important roles in the ecological functioning of a healthy reef system. For both locations the importance of monitoring the fish populations is evident, either in order to assess the success of the CCMPA or to monitor the populations of fish around Utila as a measurement of their status and the role of fishing on the ecology of the reefs. In addition to a yearly monitoring program of fish populations on the two islands the surveys of the reefs around the Cayos Cochinos and Utila offer a unique research opportunity for the comparison of fish and invertebrate communities on contrasting reef systems. The reefs around the Cayos Cochinos having various degrees of protection from fishing pressure in comparison to Utila, where fishing is unregulated. Equally The Cayos Cochinos Islands are effectively devoid of mangroves, a highly important area for many juvenile reef fish, in 13

15 contrast the island of Utila is dominated by mangrove systems and the reefs around the island are nearly all adjacent to mangrove systems. 3.3 Methods Surveys of fish populations were done using underwater visual census (UVC) on 3 reefs each around both locations, Arena, Pelican and Timon within the Cayos Cochinos, and Black Coral Wall, Little Bite and Diamond Caye around Utila. Ecologically and economically important species of reef fish were surveyed (Table3.1). Transects were laid over 50m and fish populations counted 2.5m either side of the tape and 2m above as divers swam along the transect at a consistent speed. This equates to a surveyed area of 250m 2 or 500m 3 (n=8). These surveys were conducted as part of a larger project comparing fish population on reefs with and without adjacent mangrove systems. Diversity (measured through the Shannon diversity index), species number and individual numbers of fish are analysed through univariate statistics, as are populations of individual species of fish. Community structure is compared though multivariate statistics with fish counts square root transformed prior to n-mds ordination and ANOSIM analysis. Table 3. 1 Fish species identified and surveyed on the reefs around both the Cayos Cochinos and Utila Family Common name Latin name Butterfly Foureye butterflyfish Chaetodon capistratus Spotfin butterflyfish Chaetodon ocellatus Banded butterflyfish Chaetodon striatus Damsel Sergeant Major Abudefduf saxatilis Grouper Graysby Cephalopholis cruentatus Rock hind Epinephelus adscensionis Nassau Grouper Epinephelus striatus Black Grouper Mycteroperca bonaci Scamp Mycteroperca phenax Tiger grouper Mycteroperca tigris Grunt Caesar grunt Haemulon carbonarium French Grunt Haemulon flavolineatum Spanish Grunt Haemulon macrostomum White Grunt Haemulon plumieri Blue Stripped Grunt Haemulon sciurus Black margate Anistremus surinamensis White margate Haemulon album Porkfish Anistremus virginicus Parrotfish Redband Parrotfish Sparisoma aurofrenatum Redtail Parrotfish Sparisoma chrysopterum Redfin Parrotfish Sparisoma rubripinne Stoplight Parrotfish Sparisoma viride Snapper School master Lutjanus apodus Yellowtail Snapper Ocyurus chrysurus Surgeon Ocean Surgeon Acanthurus bahianus Blue Tang Acanthurus coeruleus 14

16 3.4 Results Fish population properties and individual species Diversity of fish was higher on Utila than the Cayos Cochinos, as was the number of fish species and individual fish, with an average of 8 species and 27.5 individuals per transect on Utila compared to 4.3 species and 10.5 individual fish per transect around the Cayos Cochinos (Table 3.2). Table 3.2 Number of species, individuals and diversity of reef fish populations on the reefs of Cayos Cochinos and Utila. Standard errors (se) are given (n= 8). Cayos Cochinos Utila Number of species se Number of individuals se Shannon Diversity se Of the fish species surveyed populations of Grunts, Parrotfish and Snappers were all more abundant on Utila than on the Cayos Cochinos reefs, as are Sergeant Major Damselfish. Butterfly, Grouper and Surgeonfish are all equally abundant between locations. Community composition comparison The fish community differs between Utila and the Cayos Cochinos when analysed by individual species (R=0.289, p = 0.01), or with fish counts grouped into families (R = 0.327, p = 0.01) (Figs 3.1, 3.2). Figure 3.1 n-mds ordination of fish community composition based on individual fish species counts based on Table3.1 15

17 Figure 3.2 n-mds ordination of fish community composition based on fish counts grouped into family groups based on Table Conclusions The fish population on the reefs of Utila are healthier than those around the Cayos Cochinos, with higher numbers of individual fish, more species and more diversity. Given the protection given to the fish around the Cayos Cochinos by the CCMPA this was unexpected but may highlight the importance of a mangrove system adjacent to the reefs. Of the species with higher abundance on Utila than the Cayos Cochinos Grunts, Parrotfish and Snappers are known to utilise mangroves as nurseries, although they are more generalist and will use seagrass systems as well. Groupers vary between species with some but not all species using mangroves as nurseries. Their equally low abundance at both sites may well be an indication that they are being over fished in both systems and the proximity of mangroves to the reefs at Utila is not providing them with a refuge against this pressure. Butterfly fish populations would be expected to be higher around Utila as their juvenile stages are very commonly found in mangroves, however their equal abundances at each sites indicates that maybe another variable is dictating their population levels, possibly food supply or predation. The results from the 2008 season give differences in the composition of the reef fish communities between the two locations. The possible reasons for this are discussed, however it is likely that a longer term monitoring program with more detailed analysis and sampling within the two locations in the future will give a much stronger indication as to what factors are dictating the fish populations. This can then be used to provide a fully valid assessment of the CCMPA and assess how the beneficial influence of the mangrove systems on Utila rivals that of the fishing pressure placed onto the same reefs. 3.6 Publications Harm JH, Kearns E, Speight MR (submitted) Differences in coral-reef fish assemblages between mangrove-rich and mangrove-poor islands of Honduras Proceedings of the 11th International Coral Reef Symposium, Ft. Lauderdale, Florida, 7-11 July

18 Shrives, J.P., Cowie, G.L., Thompson, P.A., Riley, J.S. and Speight, M.R. (2008) Integrating oceanography and marine ecology: What effect does the Río Aguán have upon the benthic reef community of Los Cayos Cochinos, Honduras? Oral Presentation RCUK 2008 Shrives, J.P., Lea, J.S.E. and Speight, M.R. (2008) How Does Black Band Disease Affect The Benthic Ecology of Reefs in Los Cayos Cochinos, Honduras? Poster Presentation RCUK Mullier, T.W. and Shrives, J.P. (2008) Ecological distribution, demography and host specificity of cleaner shrimp in the Cayos Cochinos, Honduras. Poster Presentation RCUK Shrives, J.P. (2008) Safeguarding the Reefs of Cayos Cochinos, Honduras. ADM, Issue 29 Shrives, J.P., Lea, J.S.E. and Speight, M.R. (in prep) Faunal Associations with Black Band Disease in Cayos Cochinos Honduras. For submission to Coral Reefs Shrives, J.P., Lea, J.S.E. and Speight, M.R. (in prep) Spatial ecology and succession dynamics of Black Band Disease in Cayos Cochinos Honduras. For submission to Marine Ecology Progress Series or Coral Reefs 17

19 4. Sea Urchin Ecology Research Group Personnel Senior Scientist - Project supervisor - Dissertation projects - Dr. James Saunders - Operation Wallacea John Shrives - Oxford University Edward Bridge - Lancaster University Sophie Wells - Oxford University Catherine Hall - Oxford University 4.1 Introduction to the group The Sea Urchin Research Group is based on both the Cayos Cochinos and Utila, conducting monitoring of population numbers and research into the ecology of the urchin species in the area. Urchins could be considered one of the most important groups of species on the reefs and as such the group is involved in a wide variety of projects. 4.2 Project introduction and rational Sea urchins hold a very highly important role within the ecology of coral reefs, acting as one of the main grazers of algae and ensuring that a low algal density is maintained on the reefs and corals dominate. Without such grazing the potential is for algae species to grow unregulated and smother and eventually kill corals, leading to a phase shift from coral dominated to algal dominated reefs. There are four dominant species of urchins on Caribbean reefs, the long spined, reef, rock boring and pencil. Of these the long spined urchin (Diademia antillarum) was the largest and most significant grazer. However, in 1983 an as yet unidentified disease decimated the populations of the long spined urchin throughout the Caribbean. Mortality rates were between 95-99%, with 99.9% recorded in some locations. Urchins live for 100+ years so regrowth of the populations has been slow and indeed absent in some areas. The consequences of this mass mortality (the largest ever recorded in the marine environment) are varied. The majority of reefs have maintained coral dominance, due in part to increased grazing by other urchins and herbivorous fish species compensating for the loss in the long spined urchin. However, many reefs have undergone a phase shift and are now dominated by algae with severe ecological and economic consequences. The main example of this being the Jamaican coral reefs that are now nearly all algal dominated and as a result both the dive tourist and fishing industries have been heavily impacted. The reefs around the Cayos Cochinos and Utila have so far maintained coral dominance, but long spined urchin populations remain low and therefore the reefs remain highly vulnerable to a future phase shift to algal dominance. It is for this reason that a long term monitoring program of urchin populations and density has been run on Cayos Cochinos for several years and recently established on Utila. This program aims to assess if and how urchin populations are changing, determine the rate of increase of the long spined urchin population and potentially offer a warning sign if populations of any urchin species start to drop. In addition to these surveys the ecology of the urchin species needs to be studied so we can better understand the role of urchins in reef ecosystem dynamics and use this information in management practices that will ensure against a future phase shift. These projects included; 18

20 Studying the feeding preferences of the reef urchin Given the removal and subsequent low populations of D. antillarum it may have been expected that the population of one of the smaller species of urchins would increase due to the competitive release of its food source. As this appears to not have happened it is questionable as to weather the remaining urchins feed off the same type of algae as D. antillarum. To assess this a trial experiment of feeding preference of the most abundant urchin on the reef was established. Investigating the relationship between D. antillarum density and parrotfish abundance On many reefs the recovery of D. antillarum is slow or non existent, the reasons for this are unclear but it is possible that populations of other species have grown to compensate for the increase in available algae and their dominance is now limiting the grow back of D. antillarum. Parrotfish are among the major herbivores on the reefs and it is possible that their abundance and feeding is limiting D. antillarum development. To assess this a project will look at the relationship between populations of parrotfish and D. antillarum on several reefs around the Cayos Cochinos. Microscale habitat preference of D. antillarum on the reefs around Cayos Cochinos Regrowth of the populations of D. antillarum is not uniform around the reefs of the Cayos Cochinos. The reasons for this are unclear, this project investigates the microscale variation in habitat on the reefs to determine if there is a preference for certain habitat types for the regrowth of D. antillarum populations. 4.3 Methods Urchin Surveys 14 reefs were surveyed around the CCMPA (Fig 4.1), these reefs have been surveyed in previous years and the same protocol was replicated this year. This involves counting all urchins within a 15m x 2m transect (30m 2 ) (n=6). Reefs were surveyed by snorkelling at depths between 1-2m. The reefs on Utila are deeper than Cayos Cochinos so Scuba was used to survey the reefs at about 4m deep. This limited the length of survey time so transects were shortened to 10m x 2m (20m 2 ) (n=6) and only 4 reefs were surveyed. One way ANOVA was used to compare the densities of urchins between and within reefs. 19

21 Figure 4.1 Map of the Cayos Cochinos Archipelago with reefs surveyed for urchin populations highlighted Urchin / parrotfish interactions and microscale habitat variation surveys The methodologies for the two projects were combined and conducted at the same time. At 5 of the 14 sites around the Cayos Cochinos the reefs were surveyed using a 3m x 3m grid (9m 2 ) (n=6). Initially the area was marked out and observed for 20 minutes to count the number of parrotfish in the area. Subsequently the habitat within the square was measured using a variety of habitat variables, coral and algal coverage and substrate type using the Habitat Assessment Score (HAS) protocol devised by Gratwicke and Speight (1995) (Table 4.1). Counts of D. antillarum were also made in the square. Individual habitat properties were correlated with numbers of D. antillarum using spearmen ranked correlations, before all variables were combined and run through a PCA and the value along PC1 correlated with D. antillarum to determine if a number of combined habitat variables could explain urchin numbers. 20

22 Table 4.1 Scoring criterion for the Habitat Assessment Score (HAS), based on Gratwicke and Speight (1995) Feeding preference of reef urchins The reef urchin was found to be one of the most abundant urchin species on the reefs around the Cayos Cochinos, therefore it was selected to determine its feeding preference. Individual urchins were collected, each with a test diameter of 2cm, again the most abundant size found on the reefs. Urchins were placed into mesocosms for 24 hours to acclimatise before algae samples were added. Algae species used were Halimeda (H), Dictyota (D) and Lobophora (L), three of the dominant species on the reefs. Algae samples were dried and weighed prior to being attached to a small rock with an elastic band and placed into the mesocosms. Treatments included a single samples of algae; H, D and L to determine how much algae the urchin would eat without choice, paired samples; HD, HL and DL to see if the urchins would choose one type of algae over another, and all species together HDL, again to determine if urchins had a feeding preference (n=6, with equal number of controls with algae but no urchins for each replicate). After 24 hours the urchins and algae were removed and the algae dried and weighed again to determine if there had been any change in weight. The change in weight was obtained by subtracting the weight of algal after the experiment from the original weight. Any change was expressed as a percentage change from the original weight to compensate for differences in the weights of the three algal species. For single algae trails the changes in weight was compared between urchin and control treatments through a one way ANOVA, while trials with 2 or 3 species of algae were analysed using a two way ANOVA with algae and treatment as variables. 21

23 4.4 Results Urchin abundance Utila Densities of the 4 species of urchins varied across the sampled sites, with D. antillarum density very low at all sites. Despite differences between sites, numbers of reef, rock and pencil urchins were relatively consistent within each site, with the exception of reef urchins at lighthouse reef which had more urchins equivalent to an order of magnitude compared to the other species. Apart from this unique result Coral View generally had more urchins than the other sites (Fig 4.2). Figure 4.2 Density of 4 species of urchins on the reefs around Utila, numbers given as counts per 30m 2. Cayos Cochinos Urchin populations around the 14 reefs surveyed around the Cayos Cochinos varied considerably in both number and dominant species (Fig 4.3). Dominance of one species of urchin was found on many of the reefs although the species varied. On several reefs the rock boring urchin was highly dominant (reefs 1, 3, 7, 10, 11, 12, 13 and 14). However, on reefs 2 and 6 the reef urchin was most abundant and 8 and 9 had high densities of long spined urchins. Densities also varied considerably with over 100 urchins of the same species found on some reefs (3, 7, 11 and 13) while on other reefs numbers were considerably lower for all species. Several reefs had relatively high numbers of long spined urchins while other reefs the urchin was still absent Urchin/Parrotfish interactions There was no relationship between the number of urchins and parrotfish within a plot, R = , p = (Fig 4.4). 22

24 Figure 4.3 Urchin densities (per 30m 2 ) of 4 urchin reef species on the reefs of Cayos Cochinos. Figure4.4 Comparison of Urchin density and parrotfish numbers on selected sites around the Cayos Cochinos. 23

25 4.4.3 Microhabitat preference There was no individual habitat variable that correlated with the abundance of D. antillarum on the reefs around the Cayos Cochinos. PCA s of habitat variables and coral/algal type coverage both gave no positive correlation with numbers of D. antillarum (Fig 4.5). Figure 4.5 Principle Component Analysis (PCA) of habitat variables assessed through the HAS protocol (Table 4.1). Densities of D. antillarum (per 9m 2 ) are represented by sized circles, scale given on key Feeding trials Both Halimeda and Dictyota trails produced a difference in weight loss between urchins and controls although unexpectedly the largest loss in biomass was in the control mesocosms for both species (Fig 4.6). Lobophora biomass did not change between treatments. 24

26 Figure 4.6 Change in weight of three algal species placed into mesocosms with individual reef urchins for a period of 24 hours. Control treatments had no urchins. As with the single trails both Halimeda and Dictyota had a larger loss in biomass in the control treatments than in urchin treatments (Fig 4.7), Combining Halimeda and Lobophora gave no difference with between urchin and control treatments for either species but there was a larger loss in biomass overall from Halimeda than Lobophora, indeed, on average Lobophora increased in biomass over the 24 hour trial. When combined together both Dictyota and Lobophora lost more biomass in treatments with urchins, although Dictyota lost more than Lobophora. Finally when all the species of algae were combined Dictyota lost more biomass than the other species although equal amounts were lost in urchin and control treatments. Both Halimeda and Lobophora lost less biomass than Dictyota and lost more in the urchin treatments than controls. 25

27 Figure 4.7 Change in weight of three algal species placed into mesocosms with two different species of algae present in each trail. An individual reef urchin was placed into the mesocosms for a period of 24 hours. Control treatments had no urchins. 4.5 Conclusion Survey results A comparison of the urchin numbers between the two sites displayed a similar pattern, both sites have reefs with very high (100+) numbers of urchins, and equally sites with low densities. Dominance by a single species was more common around the Cayos Cochinos than Utila. This may be due to the variability between sites, as the 4 sites on Utila are of a similar nature on the south shore of the island. In contrast the reefs around the Cayos Cochinos offered a variety of habitats, the nature of which may favour one species over another. However, this was not reflected in the habitat survey measurements. 26

28 The data collected will form part of a long term monitoring program which can be used to assess the health of the urchin populations each year, monitor any growth in the populations of long spined urchins, give an early indication of potential drops in the populations of any species of urchins and possibly give data for an impact assessment of events such as hurricanes or severe pollution and disturbance Habitat preference The unequal recovery rate of D. antillarum throughout the Cayos Cochinos MPA does not appear to be linked to any of the environmental or biological parameters measured within the sites. It is quite possible that the limited number of variables measured did not cover the particular factor that influences the abundance of D. antillarum, or equally it may be that regrowth is idiosyncratic and not linked to habitat or biological parameters Urchin/Parrotfish interaction As with the habitat data there was no indication that densities of D. antillarum were influenced by the number of parrotfish on a reef. It is possible that the two types of herbivores are feeding on different types of algae and therefore do not interact, equally it may be that different species of parrotfish feed on different types of algae and this was missed due to the methodology only counting total parrotfish. A more detailed study on the potential interactions between the two herbivores would be interesting as variables such as the abundance of other species of urchins, species specific parrotfish counts and species specific algal coverage may highlight a more intricate interaction Feeding preference The results from this experiment are unclear when trying to assess feeding preferences of the reef urchin. In the single species trails of Halimeda and Dictyota there is actually more loss of biomass in the controls than the urchin treatments, while there was no change with Lobophora. This was unexpected and implies that the urchins were not feeding on the algae, or possibly the urchins were providing waste nutrients on which the algae was growing, rather than just decaying in the control treatments. The implications for this are that the remaining trails with multiple algal species have to be considered dubious as it would appear the urchins were not feeding on the algae and changes in biomass are related to external variables that have not been considered in this experiment, possibly related to the reaction of each algal species to its sampling. 4.6 Publications Hall, C. M., Shrives, J.P., Speight, M.R and Saunders, J. (2008) Sea urchin ecology on the shallow reefs of Cayos Cochinos, Honduras, with particular focus on Diadema antillarum recovery. Poster Presentation RCUK Shrives, J.P. and Speight, M.R. (in prep) Assessment of the 2007 post-hurricane Dean stranding of sea urchins upon the beaches of Los Cayos Cochinos, Honduras. For submission to Coral Reefs 27

29 5. Mangrove Ecology Research Group Personnel Senior Scientist - Fish Research Scientist - Dissertation projects - Dr. James Saunders - Operation Wallacea Jessica Harm - Oxford University Ben Thorne - Lancaster University Hayley Geldart - Lancaster University Chris Dixon - Lancaster University Tara Seez - Nottingham University 5.1 Introduction to the group Utila contains extensive mangrove systems that are an integral part of the functioning of the marine ecosystem. However these are under considerable threat from development on the island, especially related to the growing dive tourist industry. The Mangrove Ecology Research Group has a variety of aims, measuring the exposure of areas of the mangrove system to pollution and disturbances, assessing how this related to the health of the mangroves themselves and also various functions of the mangrove systems, including acting as fish nurseries for juvenile reef fish and as coastal defence and sinks for waterborne sediment and pollution. 5.2 Project introductions and rationales There are 4 main lagoons on Utila (Fig 5.1), two each on the north and south shores. Of the four, the two on the south shore have experienced high levels of disturbance as a result of the development of the island, and in particular the dive industry. In contrast, the two lagoons on the north shore are relatively untouched, indeed one, turtle harbour, is established as a protected area, with only researchers allowed to enter. The two lagoons on the south shore, Big Bite Pond and Oyster Bed Lagoon, are subjected to varying types and scales of anthropogenic impact. Big Bite Pond is located on the very east of the island, near the main population centres. In particular a slum type area, known as Campanada, which has grown as a result of the influx of Hondurans from the mainland who work in the tourist industry. This area has grown through the extensive removal of large areas of mangroves and houses built here have little or no facilities for removing waste. The result of this is a high level of sediment erosion and an expected high level of organic pollution within Big Bite Pond. Oyster Bed Lagoon is used by a lot of the higher end hotels on Utila and as a result is not expected to suffer from the levels of organic pollution experienced in Big Bite Pond, however the hotels bring with them a high level of boat traffic disturbance and the development of the hotels and additional ongoing projects require extensive dredging of the lagoons. The result of which is a system subjected to high levels of physical disturbance. In contrast, the two lagoons on the north shore, Rock and Turtle 28

30 Harbour are relatively untouched, especially Turtle harbour which is protected by local laws and access is prohibited unless for sanctioned research. Projects being run by the mangrove research group involve assessing the pollution and disturbance levels within the lagoons and the subsequent effect this has on the health of the mangrove systems. This data will then be used as a background of system health from which other studies of mangrove system functioning related to health can be performed. Currently this involves assessing the functioning of mangroves as a nursery for juvenile reef fish species and assessing the ability of mangroves to stabilise sediment and sequester pollutants. Figure 5.1 Utila with locations of the four sampled lagoons highlighted. Images taken from Google Earth. 29

31 5.3 The effects of pollution and disturbance on the health of mangrove systems Introduction Marine sediment systems provide a valuable way of measuring the long term health of a system. Deposited sediments often sequester pollutants from the water column that are adsorbed onto the sediment surfaces. This means studying the sediment allows a good measurement of long term pollution exposure within a system that may not be possible from sampling the water given its short residency time within the system. Likewise analysis of the density and resistance to erosion of sediments is a good indicator of the level of physical disturbance experienced by the system. A project was devised to sample the sediment from the lagoons around Utila to look for indicators of system health, this was combined with a large scale survey of the mangrove trees in the lagoons to determine if sediment properties, pollution and disturbance correlated with the health of the mangrove trees Methods Sampling strategy Sample sites were selected every 100m around the edges of the four lagoons. Access to the lagoons was done by kayaks and hand held GPS locators were used to find the sites. Mangrove health The health of the mangrove trees surrounding the lagoons was measured at the sample sites through counts of primary, secondary and tertiary root number. Additionally counts were made of the number of roots that had penetrated the water surface but not reached the ground and their status (living/dead) recorded. Survey of surface sediment properties Approximately 70 sites were sampled around the edges of the 4 lagoons, in addition to open water sediment samples from near the mouths of the lagoons, giving a total of approximately 200 sediment samples. Sediment cores (diameter 5cm, depth 5cm, volume 100cm 3 ) were pushed into the upper sediment in the shallow water (<30cm) and the base secured before removing the sediment core. Measurements of ph, salinity and temperature were taken from the sediment before the cores were transferred to sealed plastic bags for transport back to the laboratory for subsequent analysis of water content, conductivity and dissolved oxygen. Missing data Due to a series of equipment failures several measurements of sediment properties were not taken in some of the lagoons, these are mentioned in the relevant result sections. Statistical analysis Sediment properties were compared between lagoons using a one way ANOVA after assumptions of normality were tested. A tukey post hoc test was used to identify differences between lagoons. 30

32 5.3.3 Results Mangrove health There were more dead roots than living in all of the lagoons, of these the number of living roots in BBP was lower than that in OBL, while TH had a very high variation so was similar to both (Fig 5.2). The number of living roots in OBL and BBP were the same and both higher than that found in TH. There was no difference between the numbers of primary, secondary and tertiary roots within each lagoon. For each lagoon the tertiary roots far outnumbered the secondary and primary roots. Figure 5.2 Numbers of living and dead submerged rot tips per site in each of the 3 lagoons Sediment properties The ph of the sediments fell in to two groups, higher values for the sediments in the open water, turtle and rock harbours, and lower values in OBL and BBP (Fig 5.3). This pattern was also found in measurements of salinity (although open water sediments were not tested) with higher salinities in Turtle and Rock Harbour (Fig 5.4), while the reverse was found in measurements of water content. With higher water content in the sediments of OBL and BBP in comparison to TH, RH and open water (Fig 5.5). 31

33 Figure 5.3 ph values taken from sediments in the 4 sampled lagoons and open water Figure 5.4 Sediment salinity values taken from sediments in the 4 sampled lagoons on Utila 32

34 Figure 5.5 Surface water content levels of from sediments in the 4 sampled lagoons on Utila Conductivity measurements were taken in the sediments of TH, BBP and OBL. Of these BBP had a highly elevated conductivity compared to the other two lagoons (Fig 5.6). Figure 5.6 Conductivity of the sediments from three laggons on Utila Temperature varied between the lagoons, with both BBP and TH having higher values than OBL and RH. Again, open water sediments were not sampled (Fig 5.7). 33

35 Figure 5.7 Temperature of the surface sediments from the four sampled lagoons on Utila Dissolved oxygen measurements were only taken from TH and BBP, with TH having a higher value than BBP Discussion The health of the mangroves differed between lagoons when measured through counts of living and dead roots. This was not reflected in the number of primary, secondary and tertiary roots. For a difference to be found in the nature of the roots then it would be assumed that an unhealthy plant would not be growing as much as a healthy tree and as such would have less primary and secondary roots as these would be indicative of recent growth. However, it is possible that either this assumption about growth patterns is wrong, or equally that the growth rate of mangroves is slow, and given that the development on Utila has mostly occurred in the last 10 years then mangroves have not been subjected to pollution and disturbance for sufficient time for the expected results to have developed. It is possible that living and dead root tips are therefore a better indicator of current mangrove health as the root tips are more recent growths and their status would be affected by recent pollution levels. If this is so then the low number of living roots in Big Bite Pond may be a result of the pollution within the lagoon. Measurements of sediment properties were affected by the failure of certain pieces of equipment, leaving several uncertainties. However findings of particular interest were those of the ph, salinity, water content and conductivity. The ph was higher in the two southern lagoons while salinity displayed the opposing pattern. This may be a result of the very limited cycling between the southern lagoons and the sea compared to that of the northern lagoons. Mangrove trees produce high levels of organic matter, in addition to requiring specific properties from the water. The combination of these may influence the local water properties. Given the limited cycling in the lagoons this influence may not be flushed out of the water and instead influence the sediment properties. Similar processes may have resulted in the high conductivity in Big Bite Pond compared to Turtle Harbour where the mangroves were influencing the sediment properties, the limited sampling in Oyster Bed Lagoon means analysis of its values is unreliable. Surface sediment water content, used as a measure of compaction, and a proxy for disturbance is highest in the two southern lagoons. This may be a consequence of the disturbance caused by dredging and boat traffic, however, it may also 34

36 be that the higher levels of background disturbance in the northern lagoons, compared to occasional disturbance in the southern lagoons, causes the removal of unconsolidated sediment leaving only the highly consolidated sediment. The health and status of the mangrove trees varies within the lagoons, and the unhealthy trees found in the Big Bite Pond were expected, especially compared to those in Turtle Harbour. The environmental measurements of sediment properties gave some indication of why this may be, with the differences in properties between lagoons, although no direct link could be made. This is possibly due to the large scale nature of the analysis with more specific patterns of sediment properties and mangrove health isolated to sections within each logon, rather than the lagoon as a whole. Further analysis of the data will be performed to identify areas of particular interest and these can be highlighted for future research. 5.4 Sediment stabilisation and sequestering Introduction All marine sediments are a composition of a variety of solid material, such as sediment particles, organic matter and detritus. The spaces in between these solid components are filled with water, a measure of which is the water content of the sediment. Compact sediment has a higher level of solid material per volume and therefore has less space for water to fill and subsequebtly a lower water content. As a result the water content of sediment is a measure of its compaction. Marine sediments vary in their stability, a measure of their resistance to erosion, this is a highly important measurement and property of coastal sediments as it is an indication of the erosion potential of the sediment. Mangroves are vital for the stabilisation of coastal sediment systems as their root systems promote sediment deposition and compaction, resulting in an increase in sediment stability and resistance to erosion, something that is vital in hurricane areas. As such the stabilisation of sediments can be considered a function of mangroves systems. Associated with this sediment deposition is the sequestering of water borne pollutants that are often adsorbed onto suspended sediments. Physical disturbance of the sediments either prevents sediment compacting once settled, or lowers the volume of water borne sediment settling on to the substratum in the first place. In mangrove systems disturbance can therefore lead to a lowering of the compaction of sediments within the systems. Measuring the compaction of sediments is therefore a good indication of the level of disturbance in a system Method Sediment samples were taken around the edges on OBL and BBP (Fig 5.8). Each sample site consisted of three cores (diameter 5cm) taken to a depth of 10cm. The cores were then sectioned at depths of 1, 2, 4 and 6 cm, giving 5 different sections. The water content of each section was taken in the laboratory and the results from the three depth sections at each site averaged to give a reading for the site. ANOVAs were used to compare the water content between depths and lagoons. 35

37 Figure 5.8 Sample locations of sediment cores taken for depth profiles of water content in Big Bite Pond (Left) and Oyster Bed Lagoon (right) Results The water content of sediments in Oyster Bed Lagoon was lower than that of Big Bite Pond, however there was no change in water content with depth of sediment (Fig 5.9). Figure 5.9 Depth profiles of average sediment water content of the two lagoons on the south shore of Utila, Big Bite Pond (BBP) and Oyster Bed Lagoon (OBL) Conclusion An expected decrease in water content with depth was not found. It was expected as the deeper sediments would not be exposed to the same level of disturbance as the higher sediments and as such would be more settled and consolidated. That this was not found is an indication that either the depth of the cores taken was not sufficient to cover the depth of sediment required for this consolidation to occur, or that the variation within the lagoons was too high for a direct comparison of the two lagoons and more specific, localised patterns may be more important. 36

38 As sediment does not appear to be consolidated at depths down to 10cm then this implies that there is a high volume of very unconsolidated material in the lagoons. This is important as the nature of this sediment makes it very prone to being eroded. The consequences of such erosion are severe, both for the status of the coastline but also the potential resuspension of that much sediment could lead to a huge input of sediment on to the reefs that would be highly stressed by such an input. Given the importance of mangroves in stabilising and consolidating the sediment this needs to be studied further as if there are certain areas of the lagoons with sediments with specifically high water contents then these will be the areas most prone to erosion and require the most projection. 5.5 Relationship between mangrove system health and function as a reef fish nursery Introduction Mangrove systems are well recognised as a vital component of the life cycle of many reef fish, including many commercially and ecologically important species. There is a large supply of suitable food in addition to the complex three dimensional root system and shade providing a good refuge from predation for juvenile fish that then migrate to the reefs once large enough. Previous studies have compared the nursery function of healthy mangroves in comparison to destroyed systems, however little work has been done looking at the levels of functioning in disturbed systems, especially related to anthropogenic disturbance. A study of Oyster Bed Lagoon was performed assessing the populations of juvenile fish in various parts of the lagoon with different health statuses Method Figure 5.10 Deploying a minnow trap at the mangrove edge Three sites were selected within the lagoon; both the east and west sides of the lower lagoon and one site in the upper lagoon (Fig 5.1). Physical and environmental measurements of these sites were made, including root size and density, tree health and water quality. Two types of traps were used to sample the juvenile fish communities at each site, minnow traps and light traps. Minnow traps are small net cages with a narrow funnel opening allowing fish easy access into the trap but ensuring they remain in the trap once inside (Fig 5.10). At each site 20 traps were positioned along the edge of the mangroves at 5-10 metre intervals level with the prop roots. Traps were deployed on three occasions over the summer. Bait is required to lure the fish in to the traps although there is debate as to what is the best substance for this. 37

39 Instead a standard four day cycle was performed in each trap with no bait for 24 hours, coconut for 48 hours and crab meat for the final 24 hours. The traps were emptied of fish every day so the success of each bait in attracting fish into the traps can be assessed. Light traps were constructed where florescent bulbs were used to attract juvenile fish (Fig 5.11). These traps were deployed at each of the three sites at sunset and collected the following morning (n=5), traps were deployed three times, twice during full moon and once during a new moon. The taps were positioned 5m from the edge of the mangroves to allow sufficient depth for the traps and >15m apart to avoid light overlapping from adjacent traps. Figure 5.11 A light trap After traps are picked up, all fish larvae are removed, preserved in 70% alcohol and identified under a dissecting microscope. Snappers were identified to the species level while remaining species were identified to the family or genus level. DNA analysis can be used to identify to the species level if needed Results Minnow traps caught 11 species of fish and 2 juvenile fish species, Alpheus shrimp and three genus of crab were also caught. Communities between the three sites differed, with the largest difference between the west lagoon and the other two sites (Fig 5.12). There was no difference in the communities caught within site with coconut and crab meat baits, although the absence of any bait did significantly lower the number of fish caught. Figure 5.12 n-mds Ordination of juvenile fish community structure from three locations within Oyster Bed Lagoon Light traps were not as effective as the minnow traps, nor were they as effective within the mangroves as they have been shown to be on the reefs. Despite this 12 families of fish larvae 38

40 were caught, the majority of which were Engraulids (anchovies). The low numbers of fish caught prevented detailed analysis between sites, however the number of fish caught in each trap was lower when sampled at the full moon compared to the new moon. Environmental data has yet to be fully processed and analysed Discussion The three sites within Oyster Bed Lagoon each had a unique fish community, unfortunately without the environmental data it is not possible to draw conclusions as to why this may be. The relative low numbers caught in the light traps in comparison to the minnow traps implies that the traps were not as successful, rather than the fish communities being different on these sample locations. The supposition that this is due to low light penetration in the lagoons is supported by the higher catch levels during the new moon when background light would have been lowest and the relative light from the traps strongest. 5.6 Overall Discussion The mangroves on Utila are evidentially being placed under a wide variety and scales of pollution and disturbance. This is resulting in mangroves systems ranging from very healthy in Rock and Turtle Harbour, through to critically unhealthy or destroyed in Oyster Bed Lagoon and Big Bite Pond. The consequences for this on the functioning of the mangroves is still uncertain, however the initial study of fish populations within Oyster Bed Lagoon demonstrated that differences occurred in the community structure within the lagoon and the possibility that this is driven by mangrove status is worthy of more detailed study. ] 39

41 6. Herpetofauna Research Group Personnel Research Scientists Bob Reed - USGS Invasive Species Program Dr Chad Montgomery - Truman State University Scott Boback - Dickinson College, Auburn University Stephen Green - University of Kent Tony Frazier - California Polytechnic State University Mike Logan - University of Texas, Arlington Dissertation students Matthew Speed - Lincoln University Mike Haughey - Salem State University 6.1 Group Introduction In partnership with the University of Kent, Operation Wallacea surveys population surveys and research into the ecology of the herpetofauna within the Cayos Cochinos. This research group samples the animals on Cayo Menor and Cayo Mayor. The project focuses upon population assessments and ecological study of two species. The Cayos Cochinos Boa constrictor (Boa constrictor imperator) an indigenous species of snake found only within the Cayos Cochinos, and the Black-Chested Ctenosaur (Ctenosaura melanosterna), which is currently listed as critically endangered by the IUCN red list and whose distribution is restricted to the Rio Aguan Valley in northern Honduras and the Cayos Cochinos. Cayos Cochinos Boa (Boa constrictor imperator), Photo by Stephen Green 6.2 Bay Island Boas Project Introduction and Rational During the 1980 s the Cayos Cochinos boa, or Hog Island Boa as it is known in the pet trade, was subject to a period of intensive collection from the wild. This collection, driven by demand for these boas due to their small size and light pink colouration, led to reports of the Cayos Cochinos Boa being extirpated from these islands. Fortunately, a reduced population of animals persisted on both of the two largest islands in the Cayos Cochinos, and due to 40

42 increased levels of protection these populations are showing promising signs of recovery. The main focus of the work to date has been to; (i) Initiate a long term mark-recapture study that will provide estimates of survival, detectability and census population size (N c ). (ii) Implant boas with temperature-sensitive radiotransmitters to collect data on home range size, frequency of movement, habitat preference and thermal ecology. (iii) Conduct genetic analysis of the Cayos Cochinos population using mitochondrial DNA to construct the first phylogeny for the boas found across the Honduran Caribbean island system. (iv) Determine the level of gene flow between islands and extent of the potential genetic bottleneck caused by over exploitation for the pet trade. Other research projects being conducted include; thermal monitoring of habitat refugia using operative temperature models (OTM), investigation of Field Metabolic Rate and Water Stress using stable isotopes, and comparative head morphology and body condition of boas between islands. Future research will include an investigation of reproductive biology of the boas. These data will be essential for informing current and future management strategies for the Cayos Cochinos boa. Black-Chested Ctenosaur populations are under severe threat, The Rio Aguan Valley population is in decline and its future uncertain. The Cayos Cochinos population, therefore, represents an important refuge for this species and its protection is a conservation priority for the area. However, small insular populations are vulnerable to extinction as a consequence of stochastic events. Therefore, it is crucial that the parameters acting on this population are understood in order to implement appropriate management strategies Methodology Population Surveys Visual Encounter Surveys (VES) are performed by volunteers. Date, time, weather, location, the number of people searching, and the length of time searched is recorded for each survey. When a boa is encountered it is captured by hand and either processed in the field and released immediately or taken back to the lab for processing and released at the point of capture within 48 hours. At each capture location a number of habitat characteristics are recorded and UTM coordinates obtained using a hand-held GPS (Global Positioning System). External body temperature and ambient temperature are recorded with a heat-gun prior to capture and internal cloacal temperature is recorded immediately after capture. Boas are then measured, Snout-Vent Length (SVL) and Tail Length (TL), weighed, sexed and marked with a PIT (Passive Integrated Transponder) tag. Boas are also given a secondary form of identification by clipping the ventral scales which are retained and stored in ethanol as a tissue sample for genetic analysis. 41